I was getting changed in my bedroom after just coming out of the shower when I heard my sister and her friends outside my door saying go on it will be fun, anyway I paid no attention to them, however the door burst open and in walked my sister and her two friends, they said we are going to spank your bum, and your sister is going to help us now bend over my knee, i did as i was told I was only wearing my boxers but as I was laying over my sisters friends knee my sister walked up to me and pulled them down revealing my bare bum to all her friends they all spanked me 18 times each year then they let me go, just before they left my sisters freind said ooh you have a nice cute little bum.